Diastereoselective Petasis Mannich reactions accelerated by hexafluoroisopropanol: a pyrrolidine-derived arylglycine synthesis

A diastereoselective synthesis of pyrrolidine-derived arylglycines has been developed using the Petasis boronic acid Mannich reaction. High diastereoselectivities in the reactions of chiral amines, aryl boronic acids, and glyoxylic acid monohydrate have been demonstrated for the first time. Key to the implementation of this method is the discovery that hexafluoroisopropanol accelerates the Petasis process, reducing reaction times from multiple days to less than 24 h.     

Synthesis of arylglycines via the Dötz benzannulation reaction

Arylglycines are biologically active -amino acids. Our approach toward the synthesis of arylglycines features the Dötz benzannulation reaction between a variety of Fischer chromium carbene complexes 3 and alkyne 4. This leads to the formation of protected arylglycinols 5, which can be transformed to the corresponding N-protected arylglycines.